My skimmer (in sump) made a lot of micro bubbles at first but after about a week it mostly went away, I’m afraid as long as it’s in the tank your going to have issues with bubbles.
I had the exact tank and skimmer and it(skimmer) was a nightmare. After fighting it for weeks I finally added a CPR sump and tossed skimmer. To answer your original question - with that skimmer you're always going to have micro bubbles. Sorry for bad news.